Neuroradiology

Question 1

How do different elements appear on CT?

Answer 1

Bone and calcification are well seen
Fresh blood is bright
Ventricles are well seen (dark)
Oedema is low density
Increased cellularity (tumour) increases density

Question 2

What are Hounsfield units?

Answer 2

Measure of absorption/attenuation in a CT, giving a shade of grey

Question 3

What contrast is used in CT?

Answer 3

Iodinated contrast

Question 4

What contrast is used in MRI?

Answer 4

Gadolinium (bright on T1 weighted image)

Question 5

What is enhancement a sign of?

Answer 5

BBB breakdown (neoplasm, infection, inflammation, necrosis)

Question 6

What risks are there to contrast?

Answer 6

Anaphylaxis
Kidney injury
Gadolinium accumulation

Question 7

What is the smallest voxel size?

Answer 7

0.5 mm (512 matrix)

Question 8

What is s
The signal to noise ratio correlated to in CT and MRI?

Answer 8

CT: inverse relationship to X Ray exposure
MRI: inverse relationship to scan time and field strength

Question 9

How does haemosiderin show on T2?

Answer 9

Dark (useful for brain injury microhaemorrhages - parafalcine)

Question 10

How does methaemoglobin show on T1?

Answer 10

Very bright (intracellular shows dark on T2)

Question 11

What calibration is best for seeing haemorrhage?

Answer 11

Gradient echo/ susceptibility weighted image

Will show darker

Question 12

What is gliosis?

Answer 12

Fibrous proliferation of glia in the CNS

Question 13

Given that fluid is is fibrous how would it appear in T1 and T2?

Answer 13

T1 - would darken (less fat)
T2 - would brighten (less fat)